The invention concerns a device to regulate the rate of flow in a liquid fuel supply system of a gas turbine engine equipped with an air compressor. The said system is of the type comprising:
a volumetric fuel supply pump driven either by the shaft of the engine or by auxiliary means, PA1 a fuel intake line delivering the fuel from a reservoir to a pump, PA1 a fuel supply line directing to the combustion chamber of the engine the fuel discharged by the pump, PA1 a flow regulator element inserted in the supply line and means to assign values determined in the passage section of said regulator element (designated the principal regulator hereinafter), PA1 and a fuel return circuit connecting the fuel supply line upstream from the principal regulator with the fuel intake line. PA1 a tight enclosure divided into a first chamber and a second chamber by a tight, transverse partition wall, the first chamber being inserted in the fuel return circuit and further containing a fuel inlet orifice and a fuel outlet orifice and the secondary chamber being in communication with the chosen stage of the compressor, PA1 a first, tight, longitudinally deformable bellows located in the first chamber, fastened at one of its ends to a wall of the enclosure opposite to the fuel outlet orifice, in communication with the fuel supply line downstream from the principal flow regulator and carrying at its free end a valve, which tends to close the outlet orifice of said first chamber when the said bellows is dilated, PA1 a second, tight, longitudinally deformable bellows, containing no air and located in the second chamber, wherein it is attached by one of its ends to the same wall of the enclosure as the first bellows, PA1 finally, a lever traversing the separating wall, to which it is joined by means of a tight articulation and joining the free ends of the two bellows to which it is linked by means of articulated joints.
The control device of the invention is of the type comprising a second flow regulating element (herein designated the auxiliary regulator) inserted in the return circuit and automatic control means for the passage cross section of the auxiliary regulator. The automatic control elements are means acting on said passage cross section to maintain, while the passage cross section of the principal regulator remains within predetermined limits, the value of the pressure drop of the fuel in the passage of said principal regulator essentially proportional to the value of the pressure of the air discharged by a suitably chosen stage of the compressor.
There is known, for example, from French Patent published under No. 2,394,680, a control device of the above-described type. The return circuit contains at least two auxiliary flow regulators. One is controlled by the discharge pressure of the pump and the other by the discharge pressure of a stage of the compressor. This device is intended to prevent, in transitory operation, incidents such as the overheating or the stall of the compressor. It is a complicated layout because of the number of auxiliary regulators and the fact that said regulators include elastic return means. Its operating mode is poorly defined, as the auxiliary regulators act independently of each other.